1. Field of the Invention
The present invention relates to industrial columns and towers commonly used for reacting, distilling, separating, and extracting multiple components. More particularly, the present invention increases the capacity of industrial columns and towers through the acutely angular installation of the column or tower.
2. Description of the Related Art
Distillation is a widely applied separation technology. Distillation is continually affected by rising energy costs, thereby making increases in efficiency desirable. Commercially-practiced distillation methods operate on differences in boiling points between liquids, separating chemicals by the difference in how easily the chemicals vaporize. Distillation is ideal when the mixture is comprised of chemicals with distinct and separate boiling points. Distillation manipulates varying volatilities of components of a process fluid by applying and removing heat under high pressure or vacuum. The application and removal of heat fractionates individual components from the process fluid.
A process fluid is introduced to the distillation column and heat is gradually applied. As heat is applied to the column, volatile components in the liquid begin to vaporize and ascend to the top of the column. As the vapor ascends to the top of the column, the vapor interacts with the descending condensed liquid, thereby providing interaction between the liquid and vapor phases. Separation between components is enhanced when there is greater contact between the vapors and the liquids. Once the vapors reach the top of the distillation column, the vapor can be partitioned away from the remaining process fluid through outlet lines positioned proximate the top of the distillation column.
Liquid-liquid extraction is widely applied for many industrial purposes, including food, chemical, pharmaceutical, and refining. Liquid-liquid extraction is ideal for purification of heat sensitive materials and for recovery of products from reactions. Liquid-liquid extraction is extensively used in the hydrocarbon industry.
While distillation focuses on the boiling points of liquids, liquid-liquid extraction focuses on chemical structure. Liquid-liquid extraction operates on mass transfer between two or more immiscible phases. A first fluid solution is contacted with a second immiscible fluid that exhibits an affinity towards one or more components in the first fluid solution. The immiscible liquid extracts the components from the first fluid solution. The components in the component-bearing immiscible fluid are not as tightly bound to the immiscible fluid, thereby permitting subsequent component separation. The effectiveness of the extraction is related to the degree of contact between the immiscible phases. An increase in contact area results in an increase in extraction rate. Therefore, various improvements directed towards greater contact within the column have yielded greater extraction results.
The vapor handling capacity of a column or tower is generally proportional to the active area of the trays. The active area is defined as the cross-sectional area through which the upward flowing vapor passes. Therefore, previous attempts in the industry to increase the capacity of columns or towers have included improvements to the internal components, or more specifically, increasing the active area of the column or tower. Despite the changes made to internal components, towers and columns have consistently been installed in a vertical orientation. Due to this orientation, the walls of the column or tower are necessarily relatively thick to withstand high force winds. Further, a substantial subterranean foundation is needed to provide stability to the vertical column or tower in high force winds or earthquakes.
One alternative known in the art for increasing the capacity of a column or tower involves increasing the number of fractional trays. Mass transfer occurs when a liquid phase contacts the vapors on the trays. Increasing the number of fractional trays throughout the column increases the interaction between the liquid and vapor phases, thereby increasing the mass transfer between the liquid and vapor phases. While increasing the number of trays in the column is beneficial, the increases in capacity are limited. A specific spacing between the trays is required to facilitate proper operation of the column. If the trays are too close together or too far apart, the column may flood, thereby terminating throughput. Consequently, an increase in the number of trays necessarily increases the height of the column. Depending on restrictions in space and expense, increasing the number of trays may not be feasible.
Another alternative for increasing the capacity of a column is to increase the column diameter. By increasing the column diameter, the surface area of the trays is effectively increased, resulting in a larger active area for interaction between the vapors and liquids.
Previous attempts at modifying downcomer design have also increased the capacity of an industrial column. Downcomers facilitate movement of liquids between the trays. Trays are alternately installed throughout the contactor, wherein one portion of the tray is fixedly attached to the column in a horizontal orientation, and a second portion of the tray is free. Downcomers extend vertically downward from the free end of each tray. The position of the downcomer can affect the overall capacity of the column. Downcomers introduce inactive area within the column, wherein the species within the column do not interact. Recent improvements in the art have included modifying downcomer design to convert the inactive area into an active area, thereby increasing the overall active area. Attempts have included hanging downcomers, wherein the area under the downcomer is made into an active area, either with perforated holes or directional valves. While modifying downcomer design has resulted in increased capacity, installation and maintenance of hanging downcomers is difficult. Further, improper installation and maintenance can actually decrease the overall capacity of the column or tower.